Gavin James
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M94 - The Cat's Eye Galaxy

The Cat’s Eye Galaxy (M94) is one of the brightest galaxies within the M94 Group, which forms part of the Virgo Supercluster and contains about 20 galaxies. Only a few of these galaxies appear to form a gravitationally bound system. Most of the other nearby galaxies, including M94, appear to be moving with the expansion of the universe, receding from us at about 300 km/s.

M94 was discovered by Pierre Méchain in 1781, and catalogued by Charles Messier two days later. It is sometimes described as a barred spiral galaxy, but the ‘bar’ structure appears to be more oval in shape. M94 is estimated to contain 40 billion stars and is classified as having a LINER nucleus. Low Ionisation Nuclear Emission Regions are characterised by optical spectra that indicate the presence of weakly ionised gas.

M94 contains both an inner ring and an outer ring. These rings appear to form at resonance locations within the disc of the galaxy. The inner ring has a diameter of around 47,000 light years. It is the site of strong star formation activity and is sometimes referred to as a starburst ring, believed to have formed in a starburst that occurred less than 10 million years ago. The region contains many clusters of young blue stars. The energy for this star formation is supplied by gas that is dynamically driven into the ring by the inner oval-shaped bar-like structure. The outer ring of M94 extends to a diameter of around 84,000 light years. A 2009 study revealed that the outer ring is not a closed stellar ring, but a complex structure of spiral arms.  What appears to us as a ring is in fact a structure of two spiral arms that looks like an unbroken ring when seen from Earth. The study found that the outer ring is active. It contains approximately 23% of the galaxy's total stellar mass and contributes about 10% of the galaxy's new stars. It has been calculated that the star formation rate of the outer ring is approximately twice that of the inner ring. The outer ring was previously thought to have formed when M94 absorbed a smaller satellite galaxy or as a result of interaction with a star system. However, neither of these theories was supported by research and current thinking is that the inner ring is an oval distortion which led to the formation of M94’s peripheral ring.

In 2008 a study appeared to show that M94 contains very little or no dark matter. The study analysed the rotation curves of the galaxy's stars and the density of hydrogen gas and found that ordinary luminous matter appeared to account for all of the galaxy's mass. This result was unusual and somewhat controversial, as current models do not indicate how a galaxy could form without a dark matter halo or how a galaxy could lose its dark matter. However, this result has yet to be confirmed or accepted by other research groups and has not actually been tested against the predictions of standard galaxy formation models.

Research Assistant: Jonathan Genton




The Cat's Eye Galaxy
M94, NGC 4736
Spiral Galaxy
Canes Venatici
16 million light years
18 x 14 arcminutes
84,000 light years
1781, Pierre Mechain
12h 51m 46s
+41º 01’ 04”
Celestron EdgeHD 8"
10 nights in March & April 2019
RGB = 25 x 600s each
L = 29 x 1200s
22 hours 10 minutes


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